Brush

ABSTRACT

An improved brush formed of plastic comprises a base and a plurality of bristles molded integrally with the base, the said base and bristles having incorporated therein up to about 30% by weight of an abrasive material. The bristles are provided in a plurality of cylindrical clusters, with the bristles in each cluster being tapered from the wide bases to relatively narrow tips. By tapering the bristles from relatively wide bases to relatively narrow tips. large numbers of such integrally molded brushes can be reliably manufactured in a short period of time due to the superior metering of plastic material into the tapered bristle-forming cavities in the mold.

NM! 9, 1971 J. c MUHLER ETAL 3,618,154

BRUSH Filed Feb. 2, 1970 4 Sheets-Sheet 1 .2 6 nlllllllllllll:

INVENTORS JOSEPH CIMUHLER PflUL C. CLARK JAMES 4. FORD Filed Feb. 2,1970 J. C. MUHLER ET AL BRUSH 4 Sheets-Sheet m ILIV VENTORS JOSEPH C.MUHL ER PA UL C. C L A PK JA MES A. FORD Filed Feb. 2. 1970 LER ETALBRUSH JAMES A. FORD WMJM 4 Sheet s 3 INVENTORS JOSEPH a. MUHL PAUL c.cLARK V0 M971 J c MUHLER ETAL BRUSH Filed Feb. 2, 1970 4 Sheets-Sheet AIIVVEIVTOFS JOSEPH C. MUHLEW PAUL C. CLARK JAMES A. FORD United Stateseach Filed Feb. 2, 1970, Ser. No. 7,891 lint. Cl. A4611 15/00 US. Cl.15-1167 8 Claims ABSTRACT OF THE DISCLOSURE An improved brush formed ofplastic comprises a base and a plurality of bristles molded integrallywith the base, the said base and bristles having incorporated therein upto about 30% by weight of an abrasive material. The bristles areprow'ded in a plurality of cylindrical clusters, with the bristles ineach cluster being tapered from wide bases to relatively narrow tips. Bytapering the bristles from relatively wide bases to relatively narrowtips, large numbers of such integrally molded brushes can be reliablymanufactured in a short period of time due to the superior metering ofplastic material into the tapered bristle-forming cavities in the mold.

BACKGROUND OF THE INVENTION Field of the invention The present inventionrelates to brushes and more particularly to an integrally molded,one-piece brush, especially a toothbrush, in which the plastic materialfrom which the brush is molded incorporates up to about 30% by weight ofan abrasive material, especially a dental abrasive material.

Description of the prior art Typically, toothbrushes and other forms ofbrushes have been manufactured in large quantities through the use ofseveral complex and inter-related manufacturing steps. First, the brushhandle or base is molded, stamped, otherwise suitably formed and then,in a separate manufacturing operation, bristles or bristle tufts aresuitably mounted in the brush handle or base. Typically this operationhas involved drilling or otherwise mechanically forming suitableopenings in the handle or base in which the bristles or bristle tuftsare inserted.

While a number of integrally molded, one-piece brushes have heretoforebeen known, these prior art arrangements have been unsuitable for anumber of reasons. These prior art arrangements were particularlyunsatisfactory by reason of the complex molding equipment employed or byreason of the design thereof such that quality control and r high speedoperation would not be achieved.

Accordingly, a prime object of the present invention is the provision ofnew plastic molding techniques and new integrally molded brush designsin accordance with which the disadvantages of the prior art approachesmay be overcome and whereby simple, economical, one-piece integrallymolded brushes may be manufactured in large numbers.

In the dental health held today, toothbrushing is ordinarilyaccomplished with an inert brushing implement or device which is adaptedfor use with a dentifrice composition (either a toothpaste or atoothpowder) which contains an abrasive substance or material designedto clean the teeth i.e., to remove stains, plaque, pellicle, and dentalcalculus (tartar). While presently known dentifrice compositions havenot been Wholly satisfactory in this regard, it has been essential thatthe dentifrice contain such an abrasive material in order for anycleaning to 3,6l8,l54 Patented Nov. 9, 1971 occur. Indeed, whileso-called liquid dentifrices (i.e., dentifrice compositions notincorporating an abrasive component) have been known, they have beencompletely unsatisfactory by reason of their inability to clean the oralhard tissues.

However, as a result of the provision of insoluble mineral components(abrasives) in dentifrice compositions, the therapeutic advantages ofwater-soluble fluoride and stannous ion containing anticariogenic agentsin such dentifrice compositions has been severely limited. The insolubleabrasives exert a deactivating effect on the stannous and fluoride ioncomponents.

Accordingly, another primary object of the present invention is theprovision of a one-piece integrally molded plastic toothbrushincorporating an abrasive component capable of cleaning and polishingthe teeth.

Yet another object is to provide a brush especially adapted for use withliquid dentifrice compositions containing soluble, anticariogenicagents, but no incompatible abrasive components.

A further object is to provide a toothbrush incorporating an effectiveamount of a dental abrasive material which is the same as an abrasivecomponent of a dentifrice preparation such that hygienic and therapeuticcleaning and polishing effects of the dentifrice are complemented andenhanced by the common abrasive material provided in the toothbrushand/or bristling material.

Dental research has developed substantial evidence that beyond the ageof forty years loss of teeth is predominantly the result of periodontalinvolvement rather than dental caries. The most important single factorcontributing to periodontal disease is the accumulation of dentalcalculus (e.g., salivary tartar) on the teeth. These deposits result intissue inflammation of the surrounding gingiva, and, as the conditionincreases its severity, the supporting bone is also affected. Thesereactions lead to the destruction of the supporting structures and thesub sequent mass loss of teeth.

Heretofore, available dentifrice systems have exhibited relativelyunsatisfactory enamel polishing qualities and consequently have not beenwholly elfective in preventing the accumulation of materia alba, oraldebris, plaque, pellicle, stains, and dental calculus. While suchsystems are capable, to varying degrees, of removing materia alba, foodparticles, exogenous stains, and other tooth surface pigmentations whenutilized in ordinary daily brushings, they have not exhibited theability to remove the more resistant forms of enamel pigments and toproduce a smooth tooth surface resistant to dental calculus reformation.

Dental researchers have devoted their efforts almost exclusively toeffecting improvements in dentifrice systems by changing or altering thecleaning and polishing constituents thereof. Thus, the present inventionhas for another primary objective the enhancement of cleaning andpolishing through the use of an implement rather than dentifricesystems.

A related object is providing a toothbrushing implement having improvedcleaning and polishing performance (especially with respect to theprevention of re-accumulation of dental calculus, pellicle, materialalba, and the more resistant forms of oral hard tissue stains andpigmentations Yet another primary object of the present invention is theprovision of a dental health implement designed for use in stimulatinggingival and thereby to reduce the susceptibility of the user toperiodontal disease.

SUMMARY OF THE INVENTION The foregoing and other objects, advantages,and features are achieved with the present invention which comprises abrush formed of synthetic plastic material comprising a base and aplurality of bristles molded integrally therewith, the said base andbristles having incorporated therein up to about 30% by weight of anabrasive material. Preferably, the brush is a toothbrush in which adental abrasive material, especially zirconium silicate, isincorporated. The bristles are preferably arranged on the base in aplurality of tufts, each tuft comprising a plurality of individuallytapered bristles disposed about the periphery of a cylindrical grouping.By tapering the bristles from relatively wide bases to relatively narrowtips, large numbers of such integrally molded brushes can be reliablymanufactured in a short period of time due to the superior metering ofplastic material into the tapered bristle-forming cavities in the mold.

More particularly, where the integrally molded brush is a toothbrush,the abrasive material is preferably selected from the group consistingof zirconium silicate (ZrSiO calcium pyrophosphate (Ca P O anhydrouscalcium hydrogen phosphate (CaHPO calcium hydrogen phosphate dihydrate(CaHPO -2H O), insoluble sodium metaphosphate [(NaPO calcium carbonate(CaCO alumina (A1 tindioxide (SnO talc [Mg Si O (OH and mixturesthereof.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of atoothbrush produced in accordance with the present invention;

FIG. 2 is a bottom plan view thereof;

FIG. 3 is a right end view thereof;

FIG. 4 is an enlarged, sectional view taken substantially along line 44in FIG. 2;

FIG. 5 is an elevational view of a bristle-forming pin used in themanufacture of the brush illustrated in FIGS. 1-4;

FIG. 6 is an enlarged, fragmentary view of the bristleforming pin shownin FIG. 5;

FIG. 7 is a top view thereof;

FIG. 8 is a fragmentary sectional view taken substantially along line 88of FIG. 7;

FIG. 9 is a partially schematic sectional view taken through a moldingapparatus which may be employed in the manufacture of the brushillustrated in FIGS. 1-4;

FIG. 10 is a right-end view of the lower part thereof;

FIG. 11 is a top plan view of one-half of an alternative mold part;

FIG. 12 is a sectional view taken substantially along line '12'12 ofFIG. 11;

FIG. 13 is a sectional view of a complementary alternative mold;

FIG. 14 is a perspective view of another form of brush produced inaccordance with one aspect of the present invention;

FIG. 15 is a bottom plan view of the brush shown in FIG. 14;

FIG. 16 is a side elevational view of another form of brush produced inaccordance with the present invention; and

FIG. 17 is a fragmentary, exploded top plan view thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1-4 illustratean integrally molded, one-piece plastic brush 20 produced in accordancewith the present invention. Brush '20 comprises an elongated handle 22,a narrow neck 24, and a brush head 26, on which are integrally molded aplurality of bristle clusters 28. As best shown in FIG. 4, bristleclusters 28 comprise a plurality of individual bristles 30 disposed incylindrical fashion. Bristles 30 taper from relatively wide bases 32(adjacent brush head 26) to relatively thin, flexible tips 34 at theirfree ends. As Will hereinafter be explained in detail, the taperedbristle structure permits brush 20 to be manufactured in a high volume,automated basis with conventional injection molding equipment. Inaddition, because of the tapered configuration of bristles 30 (inaccordance with which the free ends thereof are relatively flexible),when the brush 20 is used in the oral cavity and the ends of the bristleclusters 28 brush across the gingival tissues, 21 high degree ofgingival stimulation occurs, and over time the gingival tissue becomeshyperkeratinized thereby enhancing periodontal health.

Brush 20, as well as the other brushes and bristling materialhereinafter described in detail, may be made from any number of suitableplastic materials. Typical materials which may advantageously beemployed include polyamides, such as nylon, flexible polystyrene,polyoleflns such as polyethylene and polyprophylene, acetals, urethanes,and the like. Mixtures of resins may be advantageously employed.Acetals, especially those commercially available from CelaneseCorporation under the trademark Celcon 17A, 0-121 and M- and mixturesthereof, are preferred plastics for use in producing brush 20 inaccordance with the present invention by reason of their strength,resiliency, and compatibility with abrasives as hereinafter described.

As previously noted, a special feature of the brush of the presentinvention is that up to about 30% by weight of a dental abrasivematerial is incorporated in the plastic material. The abrasive materialmay be incorporated into the plastic from which the device is molded inany convenient fashion. For example, the abrasive material may bephysically mixed with the plastic material before it is pelletized or,alternatively, plastic pellets and abrasive in suitable quantities maybe admixed in a suitable grinder prior to introduction of the plasticinto the injection molding apparatus. Substantially any such method maybe employed so long as the molten plastic reaching the mold contains upto about 30% by weight of the cleaning and polishing agent.

While up to about 30% by weight of the abrasive material may be usedwith satisfactory results, best results are achieved with about 5-20% byweight abrasive.

Suitable dental abrasive materials include zirconium silicate, ZrSiOtalc [Mg Si O -(OH) calcium pyrophosphate, Ca2P207, calcium hydrogenphosphate dihydrate/ anhydrous calcium hydrogen phosphate,

insoluble sodium metaphosphate (NaPO calcium carbonate, CaCO alumina, A10 tin dioxide, SnO and others. Mixtures of these agents may be employed.Zirconium silicate is the especially preferred abrasive for use inpracticing the present invention.

Mixtures of zirconium silicate and one or more of the foregoing otherdental cleaning and polishing agents may advantageously be employed andsuch a mixture should comprise in excess of about 1% zirconium silicateand preferably in excess of about 10% zirconium silicate, by weight ofthe abrasive mixture. Especially good results are achieved with mixturescomprising about 20% and preferably about 25% zirconium silicate (Le, a1:3 weight ratio of zirconium silicate to the other agent), by weight ofthe mixture. There is no practical maximum level for the zirconiumsilicate since as pointed out elsewhere zirconium silicate per se is adental abrasive agent in its own right.

The size of particles of dental abrasives can be expressed in a numberof different ways, one of the most common of which is mean diameter,i.e., the arithmetical average of the diameters of particles in arepresentative sample. As hereinafter utilized, the. term particle sizerefers to a mean diameter value.

Zirconium silicate is a well-known industrial abrasive which is used forthe grinding and polishing of glass and ceramics, however, prior to thesubject invention, this material had not been proposed for use as acleaning and polishing material incorporated directly in a toothbrushfor frequent and direct application to the teeth. The extreme hardnessand the abrasion characteristics exhibited by zirconium silicate (e.g.,a hardness number of 7.5 on the Mohs scale for commercially availablezirconium silicate, such as types used for grinding of glass) wouldsuggest to one skilled in the art that zirconium silicate wouldseriously damage (i.e., abrade and scratch) tooth structure and wouldthus be unsuitable for use on the teeth. However, it has beenascertained that it may safely be employed under the conditions of thepresent invention.

In accordance with the present invention, zirconium silicate, used aloneor in combination with other cleaning and polishing agents, hasparticles distributed in a range of between about and 8 microns particlesize. The preparation of suitable particle size zirconium silicate canbe accomplished by conventional techniques well known to the art.Basically, these techniques involve milling zirconium silicate ore(zircon), followed by standard screen sieving (or air separation) tosegregate the desired particle size. Various milling techniques may beutilized in order to obtain the desired surface configurations for theZirconium silicate particles. For example, particles may be prepared bya ball and hammer milling technique. Preferably, the cleaning andpolishing agent of the present invention comprises a mixture of ballmilled and hammer milled particles.

As is well known to the art, hammer mills utilize a high speed rotaryshaft having a plurality of hammers or beaters mounted thereon. Thehammers may be T- shaped elements, bars, or rings fixed or pivoted tothe shaft or to discs pivoted to the shaft. The shaft runs in a housingcontaining grinding plates or liners. The grinding action results fromthe impact between the material being milled and the moving hammers.When zircon ore is milled by an attrition technique such as hammermilling, relatively rough, jagged particles are produced. Particleshaving such jagged surface configurations function from a tooth cleaningstandpoint in a relatively superior manner as compared to more smoothlyconfigured particles.

Similarly, a ball mill comprises a cylindrical or conical shell rotatingon a horizontal axis which is charged with a grinding medium such asballs of steel, flint, or porcelain. The grinding is accomplished by thetumbling action of the balls on the material to be ground. Particles ofzirconium silicate treated in a ball mill of the character describedhave relatively smooth surface configurations and function better fromthe polishing standpoint than more jaggedly configured particles.Similar techniques can be employed with the other abrasives employedwith the present invention.

The particle size distributions for a preferred abrasive system inaccordance with the present invention are set forth in the followingexamples.

EXAMPLE I Particle size ZrSiO Weight percent 70 5 10 15 EXAMPLE IIAnother preferred abrasive system comprises a 1:1 weight mixture ofalumina, A1 0 (240 mesh) and zirconium silicate particles lying in therange of up to about 8 microns particle size.

Especially good results may be achieved with toothbrushes in accordancewith the present invention where the abrasive incorporated in the brushis also used in the dentifrice system employed with the brush.

FIGS. 5-10 illustrate the components of molds which may be employed in aconventional injection molding machine (not shown) to produce the brushsimilar to brush 20 shown in FIGS. 1-4. As best shown in FIG. 9, themold arrangement comprises upper mold part 40 and lower mold part 42.Upper mold part 4t), for reasons that will hereinafter appear, comprisesa pair of mold blocks 44 and 46, whereas lower mold part 42 comprises apair of mold blocks 48, 50. Blocks 44, 46 are mounted by means (notshown) so that they may be raised so as to be spaced apart from lowermold blocks 48, 50. Blocks 44, 46, 48, and 50 are cut away preferablythrough the use of conventional Elox equipment, to define four brushforming cavities, 52, 54, 56, and 58. When mold parts 40, 42 are closedas shown in FIG. 9, cavities 52, 54, 56, and 58 serve to define thehandle, neck, and brush head for a brush, such as the brush shown inFIGS. l4.

A plurality of parallel, vertical bores 70 are provided in mold block48, and bores 78 pass entirely through block 48 and communicate withcavity 58. A plurality of bristle-forming pins 72 are slidably fitted toclose tolerances within bores 70. As is best shown in FIGS. 5-8, aplurality of grooves 74 are spaced equidistant about pin 72. Grooves 74gradually and uniformly taper throughout their length from relativelywide and deep portions 76 adjacent the end of pin 74 to relativelyshallow and narrow rounded end portions 78 spaced away from the end ofpin 74. At their wide parts, grooves 74 nearly merge so that at theirbases the bristles of a brush (such as brush 20 shown in FIGS. l4)almost form a substantially continuous cylinder. Grooves of the desiredconfiguration (i.e., taper) may be provided in pin 74 through the use ofElox mold forming equipment.

When pins 72 are positioned in place in bores 70 in mold block 48, theends of pins 72 at which wide and deep portions 76 of groove 74 areprovided are flushed against the lower edge of cavity 58. Thus, pins 72in cooperation with bores 70 thereby serve to define a plurality ofbristle-forming cavities located peripherally and equidistant about pins72. In this manner, when the mold parts are closed (as shown in FIG. 9)and heated plastic is injected into the cavity under pressure through apassageway defined by additional cavities 80-82 provided in blocks 44,48, respectively (see FIG. 9), not only are the handle, neck, and brushhead molded, but plastic is forced into the bristle cavities so as toprovide integrally formed bristles such as bristles 30, shown in FIG. 4.Suitable gate means, not shown, are provided in the injection moldingapparatus in order to properly control metered flow of molten plasticunder pressure into the cavities in the mold parts.

In accordance with a prime feature of the present invention, because ofthe tapering of grooves 74, plastic is properly metered from cavities 58into the bristle-forming cavities and the bristles are smoothly,efficiently, and reliably formed with none of the difficultiesencountered in prior art molding devices in which non-tapered bristlesare utilized. Further, because of the precise tolerances between thediameter of pins 74 and bores 70, proper venting of the mold cavities isachieved.

After upper mold part 40 is raised away from a molded brush produced inthe foregoing manner, ejection of the molded brush from the lower moldpart 42 is accomplished in the following manner. The lower ends of pins72 are carried by a pair of blocks 90, 92 which normally rest on a baseblock 94 separated from mold block 48 by a pair of spacers 96. Suitablemeans (not shown) are designed to operate sequentially so as to causeblocks 90, 92 to move upwardly in the direction of an arrow A shown inFIG. 10 so as to cause pins 72 to move upwardly and thereby to push themolded brush upwardly out of cavities 56 and 58. When block reaches apoint adjacent to mold block 48, grooves 72 are positioned completelyout of bores 70 in block 48. One or more additional knockout pins 98(see FIG. 9) provided in bores 100 are adapted by means (not shown) tomove upwardly so as to separate the formed bristle components fromgrooves 74 in pins 72.

The ejection of the integrally molded brush and bristles from thegrooves 74 is facilitated by their tapered configuration shown in FIGS.6 and 8. Furthermore, by

reason of the provision of the previously described abrasive material inthe plastic from which the brush is molded, the separation of the moldedpart is further facilitated.

Thus, because of the configuration of the bristle-forming cavities, notonly are the bristles more rapidly and reliably formed, but likewise theejection and separation of the molded part is also facilitated. Further,as previously noted, the tapered bristles are preferable to non-taperedbristles by reason of their hygienic and therapeutic activity in theoral cavity and elsewhere.

By using upper and lower mold parts comprising separate pairs of blocksto define the handle and brush head, the same brush head may be moldedon a variety of different handles. For example, in order to mold a brushwith a handle such as that shown in FIGS. 1 and 2, mold blocks such asthose shown in FIGS. 11-13 should be employed. FIGS. 11 and 12 show anupper mold block 60 which could be inserted in the molding machinery inplace of the block 46 shown in FIG. 9 in order to obtain a manualtoothbrush handle. Block 60 thus has a handle defining cavity 62 formedtherein which corresponds to a handle of the design of handle 22 shownin FIGS. 1 and 2. Likewise, FIG. 13 shows complementary lower mold block64 having a handle forming cavity 66 formed therein. In addition, a pairof bores 68 are provided in block 64 to permit knock-out pins (notshown) to operate in removing a molded part from the cavities after theupper and lower mold parts have been separated. By means of the moldpart 104 shown in FIG. 9, a suitable attaching handle for use in anautomatic toothbrush power handle may be obtained. Thus, by merelyshifting from mold blocks such as 60, 64 shown in FIGS. 11-14 to moldblocks 46, 50 shown in FIG. 9, the same basic apparatus may be used tomold both manual toothbrushes and automatic toothbrushes. Further, thehighly sophisticated, exact tolerances required for blocks 44, 48 andthe associated bores and bristle forming pins need not be changed orduplicated to produce the two types of brushes.

FIGS. 14 and 15 illustrate a brush 110 produced in a similar manner butintended for use in a different fashion. Brush 110, which could beemployed as a hairbrush, has a relatively Wide rectangular brush headwith a short projecting handle 114 molded integrally therewith. On theface of brush head 112 are provided a plurality of regularly arrangedbristle clusters 116, each consisting of a plurality of individualbristles disposed equidistant about the periphery of a cylinder. Thesebristles taper in the same manner as the bristles on brush shown inFIGS. 14.

As will be obvious to those skilled in the art, substantially any sortof brush could be molded in the foregoing fashion and any arrangement orconfiguration of bristle clusters on the brush head could be obtained.Indeed, a relatively thin elongated brush head with bristles formedthereon in accordance with the present invention could be attached to awheel and thereby serve as a buffing brush.

Finally, depending upon the individual use to which the brush may beput, the abrasive component thereof may be omitted, but in accordancewith the preferred practice of the present invention, the abrasivecomponent is incorporated even in hairbrushes such as brush 110 shown inFIGS. 14 and 15.

A further aspect of the present invention is shown in FIGS. 19 and 20,in which is illustrated a toothbrush 150 comprising a handle 152 and adetachable brush head 154 having formed integrally thereon in accordancewith this invention a plurality of bristle tufts 156. Brush head 154 isdetachably mounted so that it may be discarded after use. Thus, apermanent handle 152 could be distributed with a number of replaceablebrush heads 154 in order that the user could have the benefit of using aclean, sterile bristle head at each brushing. Advantageously, the in- 8tegrally molded brush head 154 incorporates a dental abrasive materialas described hereinbefore.

While any suitable interlocking arrangement could be employed to attachbrush head 154 to handle 152, a preferred arrangement involves forming arecessed slot 158 in the interior of brush head 154, with a matingtongue 160 being provided on handle 152. Tongue 160 may be slidablyreceived in slot 158, with a detent locking arrangement 162, com-prisinga stud 164 formed on handle 15 2 and a recess 166 formed in anoverhanging end portion 168 of brush head 154, being provided tosecurely lock the brush head 154 in place. As noted, other interlockingarrangements can be employed so long as the above-described objectivesare achieved.

As previously noted, through the use of a toothbrush, preferably anintegrally molded, one-piece plastic toothbrush incorporating up toabout 30 of a dental abrasive material in accordance with the presentinvention, substantial and material dental health benefits may beobtained. A clean and very highly polished tooth surface may be achieved(thus reducing the accumulation and reaccumulation of dental plaque,pellicle, and dental calculus), thereby not only contributing to theminimization of periodontal disease, but also serving in reducing theincidence of dental caries. Furthermore, because of the nature of thetapered integrally molded plastic bristles, a superior implement forgingival stimulation is provided and the resulting oral health benefitsaccruing therefrom may be obtained.

These substantially hygienic and therapeutic oral health benefits havebeen experimentally verified in the following manner.

EXPERIMENTAL EVALUATIONS The superiority of the abrasive-containingbrushes of the present invention has been substantiated by the followingexperimental evaluations. A definitive laboratory cleaning testprocedure has been used to evaluate a number of toothbrushes, amongwhich were brushes produced in accordance with the present invention.This procedure (as set forth and described in Cooley et al. US. Pat. No.3,151,027) involved the use of polyester plastic blocks specificallydesigned for use in an electric toothbrushing machine. The blocks areground smooth, washed, dried, and a thin coating of black lacquer iscarefully applied to the surface of the block. The blocks are theninserted in the toothbrushing machine and brushed with the brushes for3,000 double strokes with a pressure on the lacquer surface of grams.Reflectance measurements of the blocks are then obtained through the useof a reflectometer. The cleaning values for the materials tested aregiven in Table I, on a scale ranging from 0 to 6.5, a higher valueindicating a greater cleaning ability (i.e., higher reflectance producedby greater removal of the lacquer is indicative of better cleaningability).

Enamel polishing values have also been obtained in accordance with aso-called toothbrush polishing procedure. The lingual surfaces offreshly extracted maxillary anterior teeth are reduced with the aid of adiamond disc, and the teeth are mounted by means of a low melting alloy,such as Woods metal, on hexagonal jigs constructed so as to fit themovable state of a reflectometer. The exposed labial surface of eachtooth is mounted in such a manner that the height of the contour is asuitable distance above the base of the jig. Throughout the procedure,care is taken to ensure that the teeth do not become dry in order toprevent damage of the tooth tissues. The exposed enamel surface is thendulled by exposing it to 0.10% hydrochloric acid (pH 2.2) for 30seconds. Any acid remaining on the tooth surface is neutralized byimmediately transferring the tooth to a saturated sodium carbonatesolution for 30 seconds. The tooth is then rinsed with water and blotteddry.

The maximum reflectance of the dulled tooth surface is determined bymeans of a reflectometer especially adapted to detect the changes in thedegree of polish of 9 the enamel surface. The refiectometer isconstructed so that the enamel is exposed to a beam of polarized light,and the amount of light reflected from the enamel surface is determinedby a photoelectric cell which in turn acti- 10 the radioactivitydetermined. Using this as a standard, the amount of tooth dentin removedduring the treatment can be determined by comparing the experimentalcount with the count of a standard. The results are revates agalvanometer. The smoother the enamel surface, ported numerically, witha high number indicating greater the smaller the amount of diffused andabsorbed light abrasion. Enamel abrasion has been determined by the and,hence, the higher galvanometer reading. same procedure using humandental enamel specimens. After the maximum reflectance of the dulledtooth is Cleaning and polishing values and dentin and enamel determined,the tooth is polished with a toothbrush abrasion values have beendetermined for a number of mounted on an automatic toothbrushing machinefor a abrasive-containing integrally molded plastic tooth specifiednumber of strokes. After the tooth has been brushes and forrepresentative conventional brushes. In polished, the enamel surface isrinsed with water so as to many instances, cleaning scores were obtainedusing a remove any residual particles of the cleaning andpolishdistilled water medium and, in addition, a calcium pyroing agent,and the reflectance of the enamel surface is phosphate dentifricemedium. The data, as well as the again measured with the tooth locatedin exactly the same constituents of the brushes, are reported in TableI. These position as that used to obtain the dull reading. The datasupport the efficiency of the brushes of this invenabsolute change inthe amount of reflectance between the tion as safe cleaning andpolising, especially polishing, dulled and polished enamel surfaces istaken as a measaids. In particular, the data demonstrate that withouture of the degree of polishing imparted by the prophylaxis sacrificingcleaning effectiveness and without undue abratreatment. sion,substantial polishing improvements may be achieved.

TABLE I Cone.

percent of Cleaning ratio Polishing Dentin Enamel Polishing polishingscore abrasion abrasion Type ofbrush Type ofplastre agent agent H2OCazP2O1 (H) (H20) (H20) Conventional' 1 0.62 48316 1.77i0. 1.1s 49:1;113.75i0.52 0.52 nails 3. ssio. 42 0. 5s 415:0 4. 27:10.55 2.22 0.4529.1=1=1.8 2. 80:1;0. 0.57 0. 33 22. 6:1;1.9 2. 22, 0.23 1.23 0.00 37.4514.1 2. 05 510. 54 5 2. 4s 0. 00 43. 4i9.8 2. 83:1 0. s4 5 1.11 1.8429.9i2.9 2.55:1:025 Acetal resin lzAcetal resin II (:50 mixture)" ZrSiOi5 2.11 2.18 39.9i3.4 2. 83:1- 0. 41 Atetal) resin II: Acetal resin III(50:50 mix- ZrSiOi 5 1.35 2.08 33.43131 3. 63:1:0

D0 Acotal resin III ZrSiO /A1 0 5 1. 03 0. 03 40. 0i3.4 2. 435:0. 29 Dodo zrsioi Anw 10 1.71 1.30 37. 5i4.2 2. 3010. 10

1 Standard error of the mean.

2 The Acetal resins Were commercially obtained from Celanese Corporationunder the trademarks Golcon 17A, M-90, and (3-121.

In spite of the described excellence of the toothbrushes of the presentinvention, these devices do not remove substantial amounts of oral hardtissue. Tooth dentin is frequently found exposed at the surface of theteeth near the free gingival margin, particularly in clinical caseswhere the gingivae have receded. The abrasion of tooth dentin by acleaning and polishing agent is much greater than the abrasion of toothenamel by the same agent, i.e., 10-100 times. Consequently, dentinabrasion is considered to be of greater clinical importance than enamelabrasion, and the effect of a cleaning and polishing device on dentin isused as an. important and reliable criterion in the selection ofsuitable agents. The brushes manufactured in accordance with the subjectinvention have highly satisfactory dentin abrasion characteristics, afact which is quite surprising in view of the innate hardness of thematerials.

A method for determining dentin abrasion values is as follows. Thedentin portions are separated from human central incisors and exposed toneutron radiation whereby a predetermined portion of phosphate contentis converted to P Each dentin portion is mounted in a low melting alloy,such as Woods metal, and is submerged in distilled water to be tested. Astimulator mounted in an automatic toothbrushing machine is arranged sothat it can be moved back and forth across the surface of the submergedportion of the dentin, and the pressure of this stimulator is adjustedto 150 grams. The tooth dentin is subjected to polishing action for agiven number of strokes, and removed from the water. The radioactivityof the water is then determined by conventional means. An equivalentpiece of dentin, irradiated concurrently with the dentin portion to bebrushed, is weighed, dissolved in hydrochloric acid, and

From. the foregoing it can be seen that the abrasivecontaining brushesof the present invention represent a substantial advance in the dentalhealth arts. The use of this implement permits one to clean and polishthe interproximal tooth surfaces so as to remove and inhibit thereformation of interproximal plaque, pellicle, and calculus. Likewise,it provides a safe, sanitary method for mildly stimulating the gingivaltissues. Further, through the use of the plastic molding technology ofthe present invention, superior integrally molded brushes may beobtained.

We claim:

1. In a one-piece molded plastic toothbrush comprising a brush base anda plurality of bristles projecting from and formed integrally with thebrush base, the improvement comprising the incorporation in the plasticof which the brush is formed of up to about 30% by weight of a dentalabrasive material selected from the group consisting of zirconiumsilicate (ZrSiO' and mixtures thereof with calcium pyrophosphate (Ca lPO anyhdrous calcium hydrogen phosphate (CaHPO calcium hydrogen phopshatedihydrate (CaHPO -2H O); insoluble sodium metaphosphate [(NaPO calciumcarbonate (CaCO alumina (A1 0 talc [Mg Si O (0H) and tin dioxide (SnOthe particles of zirconium silicate lying in the range of up to about 20microns particle size.

2. The improvement, as claimed in claim 1, wherein the dental abrasivematerial is present in the plastic material of the brush at a level ofabout 5-20% by weight.

3. An integrally molded plastic brush comprising:

a brush base; and

at least one cluster of bristles on the brush base, each such clustercomprising a plurality of individual bristle members positionedsubstantially equidistant from adjacent bristles in a generallycylindrical configuration; each bristle member being tapered from arelatively wide base in close proximity with the bases of adjacentbristle members to relatively narrow tips; the said brush base andbristle members being integrally molded in one-piece of plasticmaterial, and up to about 30% by Weight of a dental abrasive materialselected from the group consisting of zirconium silicate (ZrSiO andmixtures thereof with calcium pyrophosphate (Ca P O anhydrous calciumhydrogen phosphate (=CaHPO calcium hydrogen phosphate dihydrate (CaHPO-2H O); insoluble sodium metaphosphate [(NaPO' calcium carbonate CaCOalumina (A1 and tin dioxide (SnO' the particles of zirconium silicatelying in the range of up to about 20 microns particle size, beingincorporated in the plastic material from which the brush is formed. 4.A brush, as claimed in claim 3, wherein the brush base includesintegrally molded handle means.

5. A brush, as claimed in claim 3, wherein the plastic material isnylon.

'6. A brush, as claimed in claim 3, wherein the abrasive material ispresent in the plastic material at a level of about -20% by weight.

7. A brush, as claimed in claim 3, wherein the brush base is removablymounted on handle means.

8. A brush, as claimed in claim 7, wherein the brush base has a slotmeans formed therein, with mating tongue means being provided on thehandle means, detent locking means being provided for removably securingthe tongue means in the slot means.

References Cited UNITED STATES PATENTS 2,279,355 4/1942 Wilensky 15-1102,328,998 9/1943 Radford 15-l59 A 3,050,072 8/1962 Diener 15110 X3,252,775 5/ 1966 Tocci-Guilbert 51295 X 3,378,445 4/1968 Muhler 424-493,522,342 7/1970 Nungesser et al. 15-159 A X FOREIGN PATENTS 240,817 9/1962 Australia 1 6l87 590,097 3/1959 Italy 15-187 PETER FELDMAN, PrimaryExaminer US. Cl. X.R.

